Induction furnace



Aug. 1o, 192ev 1,595,971

Inventor Patented Aug. 10, 1926.

UNITED STATES PATENT OFFICE.

GIUSEPPE FACCIOLLOF PITTSFIELD, MASSACHUSETTS, ASSIGNOR TO GENERALI. ELEO- TRIC COMPANY, A CORPORATION 0F NEW YORK.

INDUCTION FURNACE.

Application and :une s, 1922. serial no. 565,932.

The present invention comprises an improvement in induction furnaces, in particular a furnace in which the charge which comprises the secondary is contained within a looped channel communicating with a reservoir which increases the capacity of the furnace and furnishes a working space for carrying out metallurgical operations.

I have provided a furnace of this type `in which the charge circulates by electromagnetic forces without endangering the continuity of operation of the furnace.

In some of the furnaces of the channel type heretofore in use, the circulation between the reservoir andY the channel has depended largely u-pon the compressive effeet of the secondary field upon the liquid charge which causes the expulsion of the liquid charge from the center of the channel with the return fiow from thereservoir into the channel at the sides of the channel. In furnaces of this type there is always a danger present. of a rupture of the secondary circuit by this squeezing action of the secondary field which is known commonly as the pinch effect In accordance with my invention, a circulation of the charge is produced by a repulsion between the primary and the secondary, and circulation occurs in a direction opposite to the How of circulation produced by the pinch effect, that is, an expulsion of charge occurs at the opposite sides of said channel accompanied by a return flow of charge at or near the center of said channel.

The embodiment of my invention illustrated in the accompanying drawings. and more fully described below, provides a looped, channel of elongated cross-section for containing the charge. This channel is symmetrically located with respect to the primary, and preferably the magnetic center of the primary coincides with the magnetic center of the secondary. This channel communicates with the reservoir at regions spaced different distances from the magnetic center of the primary, along the longitudinal axis of the secondary.4 As a result, circulation of the charge occurs, the charge fiowing from the channel into the reservoir at regions relatively remote from the primary, and a return flow occurs at regions near the primary.

In the drawings, Figs. 1 and 2 are vertical sections taken at right angles to each other of the furnace embodying my invention.

This furnace comprises a refractory container 1 providing a container 2, which is looped about the magnetic core 3, and a primary 4. In the furnace illustrated in the drawing the channel 2 assumes the shape of a loop in transverse section communieating along a side wall by the conduit 5 with the reservoir 6. Although I have shown the looped chamber as an annulus, I wish it to be understood that other axially elongated forms may be used which haye sufficient axial extent to overlap the primary 4.

There is a magnetic torce present which tends to split the secondary in two, pushing one-half to one side and the other half to the opposite side, the dividing plane being through the center of and perpendicular to the axis longitudinal of the secondary. This force is the repulsion between the primary and the secondary which is cumulative so that the element of the secondary most remote from the primary is repelled to the greatest extent causing an outward flow of the charge at the remote regions, as indicated by the arrows in Fig. 1, replacement flow occurring close to thc magnetic center of the primary, as also indicated by arrows.

The elongated shape of the secondary cross-section is the most favorable form to minimize the effect of the pinch orce which is present in all conductors carrying current. The furnace embodyin my invention, therefore, can be used wit i a relatively large power input without danger of rupture of the secondary. It is particularly well suited for the melting lof metals such as aluminum, magnesium and copper, which have a high electnical conductivity.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. The process of causing circulation or interchange of a conductive fluid charge between a reservoir and a communicating elongated loopcd channel of an induction furnace which consists in exerting an electromagnetic 'repulsive effect upon said charge from a central region outwardly, thereby causing a flow of charge from the channel into the reservoir at regions axially spaced apart accompanied by a return flow from the reservoir into the channel at an intermediate region.

2. An induction furnace comprising a furnace body constituting a reservoir and a channel having an elongated cross-section communicating therewith, and means for inducing an electric current in a conductive charge contained in said channel, said means being so located with respect to said channel that an electromagnetic expulsion of charge occurs from said channel into said reservoir from regions of said channel axially spaced apart, resulting in a return flow of charge at an intermediate region of said channel.

3. An induction furnace comprising a primary, a furnace body constituting a reservoir, and a channel adapted to contain a charge which constitutes the secondary' of the furnace, said channel being magnetically symmetrical with said primary and having a greater longitudinal dimension than said primary winding and communieating with said reservoir at regions spaced different distances from the magnetic center of said primary.

t. An induction furnace comprising a magnetic core, a primary Winding thereon and refractory walls providing a hollow or annular container surrounding a leg of said core and magnetically centered about said primary, said container being of greater dimension axially than said primary, said Walls also providing a path for the flow of a chargeeut of said channel at regions remote from the magnetic center of said secondary and the flow of charge into said channel at a region close to the magnetic center said primary.

5. An induction furnace comprising a primary winding, a furnace body providing an axially elongated container in the form of a loop in transverse section, a container communicating therewith along the side thereof, a magnetic core interlinked with said container and a primary winding of lesser axial dimensions located intermediate said Core and container with the magnetic center thereof substantially coinciding with the center of said container.

6. An induction furnace comprising refractory walls constituting a reservoir, and a looped channel communicating therewith,

a core interlinked with said channel and a primary coil on said core located within said looped channel, said primary coil being of lesser axial dimension than the channel, whereby repulsion of a charge in said channel in opposite directions will occur, re sulting in a flow of charge into and out ot said reservoir.

7. An induction furnace comprising rcfraetory walls constituting both a reservoir and a communicating looped channel and means for applying to a charge contained in said channel an alternating magnetic tield so oriented and -of such'strength that said charge will be effectively heated by induced currents and also repelled axially in opposite directions in said channel, thereby causing flow of charge from the channel into the reservoir at separated regions, with a return flow at an intermediate region.

8. An induction furnace comprising walls constituting a reservoir and a looped channel communicating therewith, a primary coil within said channel of lesser axial dimension than said channel and so located with respect to said channel that repulsion of a conductive charge constituting a secondary in said channel will occur in opposite directions away from said primary.

9. An induction furnace comprising a refractor'y furnace body providing a reservoir for the charge and an annular channel closed on itself in which a portion of the charge forms a closed secondary, said chan nel having an. elongated cross section and communicating with said reservoir at one side at its central region and ends, a primary winding of lesser axial dimensions then said channel inserted concentrically in said annular secondary channel and arranged with its center coincident, with the center of said annular channel, whereby heating current is induced in said secondary and the molten charge rcpelled from the central regions of said secondary axially in opposite directions toward the ends thereof so as to cause a flow of charge from the central region of said channel axially through said channel to said reservoir with return flow through said reservoir.

In witness whereof, I have hereunto set my hand this 2nd day of June, 1922.

GIUSEPPE FACCIOLI. 

